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2/4 Binary Code & CPUs

2/4 Binary Code & CPUs. Digital Signals digital versus analog, examples Binary Numbers Transistors: introduction Binary Code bits & bytes types: ASCII, UNICODE, EBCDIC. 0110101001101101 10010110. Digital Signals: why they are discussed.

jerome-grimes
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2/4 Binary Code & CPUs

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  1. 2/4 Binary Code & CPUs • Digital Signals • digital versus analog, examples • Binary Numbers • Transistors: introduction • Binary Code • bits & bytes • types: ASCII, UNICODE, EBCDIC 0110101001101101 10010110

  2. Digital Signals: why they are discussed. • Virtually everything in a computer runs in a digital system: data storage, communication, output on the screen, … • Everything is in its lowest form either ON or OFF, UP or DOWN, YES or NO. • Bits & bytes are combinations of digital signals and codes.

  3. Digital Signals: what are they? • Digital signals have two settings: ON or OFF. • Examples: smoke signals, Morse code, fluorescent lights, pass or fail • Anything that can be compared to ON or OFF can be a digital signal: • Magnets: north or south • Voltage: high or low • Light: light or dark • Gates: open or shut

  4. Digital Signals versus Analog Signals • Digital signals have two settings: ON or OFF. • Analog signals have ranges of settings: dimmer switches, human voices, ocean waves • Sound: Digital versus analog. • Analog is a wave: continuous, gradual • Digital is a step: non-continuous, ON/OFF Analog signal Digital signal

  5. Binary Numbers • A digital system • Can represent any decimalnumber with only two characters: 0 & 1 • Why not use decimal numbers? Computersuse digital systems (on or off) Decimal Binary 0 0 1 1 2 10 3 11 4 100 5 101 6 110 7 111 8 1000 9 1001 10 1010 11 1011 12 1100

  6. Transistors: tiny ON/OFF switches • Tiny electrical gates with two paths: 1. Control path (gatekeeper) 2. Signal path (goes through gate) • Only two possible states: gate is OPEN or gate is CLOSED. • Transistors are what makeup computer chips. • AMD Athlon chip has 22 million transistors. Image courtesy of AMD

  7. Binary Code: Bits & Bytes • Bit: a single element of code. 0 or 1. • Contraction of “Binary digit” • Byte: a collection of 8 bits. 00000000. • Possible number of different bytes: 256 00000000 00000001 00000010 00000011 0000010000000101 00000110 00000111 00001000 0000100100001010 00001011 00001100 00001101 0000111000001111 00010000 00010001 00010010 0001001100010100 00010101 00010110 00010111 0001100000011001 00011010 00011011 00011100 0001110100011110 00011111 etc.

  8. Binary Code: Bits & Bytes • Each byte represents 1 character or command. • A simple text file ( log.txt ) can be only a few hundred bytes. A spreadsheet ( book1.xls ) can be millions. • kilobyte: KB 2 to the 10th (1,024) bytes. megabyte: MB 2 to the 20th (1,048,576) gigabyte: GB 2 to the 30th (1,073,741,824)terabyte: TB 2 to the 40th (1,099,511,627,766)

  9. When is a kilobyte NOT a kilobyte? • Common usage (not exactly correct, but close) • kilobyte: KB 1,000 bytesmegabyte: MB 1,000,000 bytesgigabyte: GB 1,000,000,000 bytes terabyte: TB 1,000,000,000,000 bytes

  10. Why we don’t type in binary digits. • Codes (lookup tables) in the computer. • Each character corresponds to a byte. • As we type, the keystrokes are translated into bytes by the computer. • The computer reverse-translates to show the characters on the monitor. • Common code sets: ASCII, UNICODE, EBCDIC

  11. Code Types. • ASCII “As-key” American Standard Code for Information Interchange. • 1st half of the slots in the table are for “standard” ASCII characters. The second half contains the “extended” ASCII character set. • UNICODE uses 2 bytes/char rather than 1. • Supports many more characters (34,168). Esp. used for non-English languages • EBCDIC “eb-see-dik” Extended Binary Coded Decimal Interchange Code. • Mainly used on mainframe computers

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